It has been suggested, as taught in U.S. Pat. No. 2,813,045, to coat glassware with an organic material, such as a water soluble wax, by introducing the wax in vapor form into the cooling section of a lehr by injecting the wax in steam, introduced beneath the lehr mat or belt. The heated containers that would pass into the cooling section of the lehr are cooled by radiation and convection of air moving upwardly through louvres provided in the top of the lehr. The upwardly moving vapor cloud would pass out of the lehr into the surrounding atmosphere. With such an arrangement as disclosed in the above-referred-to patent, the vapor moves upwardly and, in effect, is blown upwardly over the glass surfaces thus avoiding any appreciable accumulation of vapor within the interior of the bottles. However, a substantial amount of vapor will necessarily escape into the atmosphere surrounding the lehr.
In a more recent patent, U.S. Pat. No. 3,989,004, apparatus for applying a substantially uniform thin lubricious coating to the exterior of glass containers is disclosed in which a separate, heated chamber is provided downstream of the annealing lehr. This chamber recirculates the air therein, over the ware placed therein. However, in this system it is necessary that the air be heated in order to provide an atmosphere which is within a restricted temperature range of between 180.degree. F. and 400.degree. F. in order for the coating material to adhere to glass surfaces. The ware, as explained, must be at a temperature which is compatible to the formation of the coating thereon.
Other methods have been suggested for applying coatings to the surface of glass articles after they have been annealed. One of these would require dipping of the ware into a liquid coating material solution or spraying such a solution onto the ware. While both dipping and spraying of the ware to provide coating have been used to a considerable degree, both have generally failed to be commercially accepted because of the lack of uniformity of the coverage or difficulty in application of the coating, excessive coating on more acceptable surfaces and inability to adequately coat closely spaced articles such as those being conveyed through an annealing lehr.
The requirement of the glassware being at an elevated temperature at the time a vapor contacts the ware has resulted in the ware being treated after the annealing has been completed. One of the features of applicants' invention is the ability to treat ware in the cooling section of the lehr itself. In order to do this with any degree of uniformity, it is necessary that the cooling section be what is termed a recirculating cooling section since this type of cooling section cools the entire lehr mat of ware to a generally uniform temperature. The uniformity of the temperature is important when coating the ware by movement of a vapor or mist of organic, non-metallic coating material into contact with the ware surface. It is highly desirable that the surface of the ware be at a temperature of between 200.degree. F. and 400.degree. F. It has been found by applicants that when the temperature is below 200.degree. F. at the time the ware leaves the cooling section, the coating produced on the ware frequently results in the ware being unacceptable from the standpoint that it will not permit adequate adherence of labels to the ware. In the event the temperature of the ware is above 400.degree. F., there is the distinct tendency for the ware to be insufficiently coated to provide the degree of lubricity which is believed necessary to provide adequate protection of the ware against scratching or abrasion in the later handling of the ware through normal filling lines.